Testing: iPad Mini Retina vs. iPad Air Displays

By Norman Chan

And a prediction about how Apple would make a bigger iPhone.

We posted our iPad Mini with Retina Display (hereinafter to be called Retina Mini) review video last week, but I wanted to share more thoughts about what I've noticed from using it, since I've been using an iPad Air as well. To reiterate what we said in the video, I don't think any normal person should buy both an iPad Air and Retina Mini, especially if they already own an iPad 3 or 4. I'm in a unique position to be in possession of both for the purposes of testing, and I can tell you upfront that having both of the new iPads does not come close to doubling the utility you would get from just having one. Not even close. In terms of app performance, battery life, and day-to-day usability, these iPads are effectively the same. It makes no sense from a single-user's perspective to delegate some tasks to a full-size iPad and others to the Mini. And since getting both, I've found myself reaching for one far more frequently than the other, and that's the Retina Mini. If someone asked me which iPad to buy today, the Retina Mini would be my recommendation.

That's not to say that the iPad Air doesn't make sense for any potential user. But the purchasing decision becomes less of weighing the strengths of the Air and Mini against each other and more about tallying the specific situations in which you would actually need a 9.7-inch screen. And in my experience both at home and on the road, I couldn't find a situation where a larger screen was essential to the task at hand. (I still think full-page comics are too small on iPad Air, anyway.) The two inches in extra screen space afforded by the iPad Air doesn't give you more room for images or text, it just makes them physically bigger than they would appear on the Retina Mini. The pixel dimensions of the two tablets are exactly the same: 2048 by 1356. The increase in pixel density (technically, spatial resolution) of the Retina Mini's screen doesn't mean that photos and text are sharper, it means they're smaller; you actually have to hold the tablet slightly closer to your eyes to resolve iOS's native UI text. For most people with normal eyesight, this isn't a problem. But it's why folks like my parents had trouble using the Retina Mini, because they thought everything looked too small compared to what they were used to on their iPad 3. So another way to think about why someone would need the iPad Air's 9.7-inch screen is because text legibility is actually hindered by the Retina Mini's smaller screen.

Think about Apple's definition of its "Retina" displays. The company claims that Retina doesn't denote a specific pixel dimension or density (denoted in pixels per inch, or PPI), but just a high enough pixel density so that the user's eye can't make out individual pixels from a normal viewing distance. That's why the iPad 3/4/Air class of devices can be called Retina even though they have a lower pixel density than iPhones--you naturally hold a tablet further away from your face than a phone. But this line of thinking works both ways: the "normal viewing distance" of a device is affected not only by the physical size of the screen, but the native DPI of its interface fonts and buttons. And since iOS 7 renders on the Retina Mini exactly like it does on the iPad Air (the OS and apps don't actually know what size tablet they're on, except that it's designated as Retina), everything is just shrunk down about 23 percent. You can of course pinch to zoom or adjust text DPI within individual apps, but native UI elements like notification bar text and iOS menus are fixed. (iOS 7 has a setting to increase font size for core Apple apps, as well as developer-supported apps, but not the springboard/home screen.)

This was of course the case with last year's non-Retina Mini as well, which was even worse because it coupled a scaled-down OS UI with a 1024x768 display. I never bought last year's Mini so can't really speak to how that affected users with poor eyesight.

The takeaway observation is readability and usability of any modern high-resolution display is a product of three factors: screen size, pixel dimensions, and text rendering. Pixel density is determined by the first two factors, but has to be balanced with text scaling for optimal readability. It's the reason why you shouldn't run Windows desktop at 100% scaling on 13-inch 3200x1800 screens (coincidentally, testing one now!), and why auto-scaling in Windows 8's Start Screen makes it look readable at most resolutions. iOS 7 doesn't have the same kind of scaling options because it's designed solely for Apple's limited hardware set. So far it's not been a problem with the two classes of iPads, but the Mini's screen size does push the limits of physical text size on a tablet.

In fact, there's one clue in the text size on the Retina Mini that might give some insight as to how Apple would a bigger iPhone if it wanted to. We're at year's end, so forgive me for making a product prediction.

Something I noticed when scrutinizing the text size of iOS 7 on the Retina Mini was that it looked strangely familiar. I knew that the Retina Mini had the same pixel density as the Retina iPhones (326 PPI), a decision attributed to production line optimization. Last year's non-Retina Mini had the same pixel density as the iPhone 3GS (163 PPI), which led analysts to speculate that Apple would be sourcing its Mini displays from the same provider of its discontinued iPhone 3GS, cutting larger LCD sheets for the tablet. That meant that when Apple pixel-doubled the resolution of the Mini for this year's Retina model, it could source the panels from its Retina iPhone display providers. Supply chain efficiency, Tim Cook's claim to fame.

But what surprised me when putting an iPhone 5 next to the Retina Mini was that there were some UI elements that rendered in exactly the same physical size, at the same DPI. The text in the notification bar, like the time and battery percentage indicator, are exactly the same size between the iPhone and Retina Mini. Same goes with the text size and menu heights of the Settings app between the two tablets. A more prominent example of this DPI synchronically is in Safari on a website without responsive or mobile designs like the New York Times homepage. Opening nytimes.com on both devices gives you a different initial rendering, which makes sense because of the different physical screen sizes and aspect ratios. But double tap a column of text to zoom in and both the Retina Mini and iPhone will zoom in to exactly the same text DPI. I find the correlation striking because iOS for iPhone and iPad are essentially independently operating systems, and as I mentioned earlier, iOS 7 is not aware of what size iPad it's running on.

That to me says that there was some foresight in the design of the Mini class of iPads to determine its 7.9-inch screen size and 23% reduction in iOS scaling so that the native UI text DPI and menus would be aligned with the text and menu size of iOS on iPhones.

Here's where I make a logical leap for prognostication. The Retina Mini and current iPhones use a similar 326 PPI display and aligned native text rendering, and the iPad Air uses a 264 PPI display that is also classified as Retina. So if Apple were to make a larger iPhone to appease a market of users who find text on the iPhone too small (like my parents, or those who buy 5.5-inch phones), it would make sense for them to use the same 264 PPI display from the iPad Air, cut to the iPhone's 1136x640 pixel dimensions. And that display would be 23% larger than the current 4-inch iPhone 5/C/S screen, making it 4.9-inches. There's your 5-inch iPhone.

Yeah, it would be a 5-inch phone with pixel dimensions of less than even 1280x720 in a market where 5-inch phones have 1920x1080 screens, but text and images would look just as good as they do on the iPad Air, which is honestly well above acceptable. Pair that larger screen and requisite larger chassis with a big battery and it's an iPhone that Apple could probably grant a ridiculously long battery life. I'm thinking 15 hours, just to throw a number out there. It's the Haswell MacBook Air approach for iPhones--making unbelievably long battery life the selling point of the device instead of screen resolution. And I think it'd be a smart decision.

Apple has been battling the perception of screen size as a premium for the past generation of iPhones and iPads. I've said it before: aggressively-priced tablets like the Nexus 7 and Kindle Fire HDX have diminished Apple's ability to market small size as a premium feature, which is something we as users are beginning to recognize. The increased portability and ergonomics of the Retina Mini makes it much more attractive than the iPad Air, and I'm sure it pains some Apple accountant that it has the lowest profit margin of any iOS device Apple currently makes. The same applies to smartphones--Apple believes that the compactness and low weight of the iPhone (without sacrificing battery life or performance) is a key advantage over other smartphones. But it can't ignore consumer perception and market forces; people want big phones. Only time will tell if Apple will hold its ground or give in to that demand, in which case they're sure to do it in flashy fashion.